330 GEOGRAPHICAL DISTRIBUTION 
peculiarity is numerically of less importance than some of the 
Subregions of the Neotropical Region, as the following table will shew 
more plainly :— 
Whole No. | Peculiar | Percentage of 
of Genera. | Genera. Peeuliarity. 
Patagonian . , ; : ; 290 46 15862 | 
Brazilian ‘ ; ‘ : : 396 43 10°857 
Amazonian . : H : : 373 27 7°238 
Subandean . : : 3 : 469 (y 15°38 
Central American . : : . 464 46 9°913 
Antillean . ‘ ; ; ‘ 140 30 21°444 
Nearctic - A é : 330* 24* 7°272 
* These numbers, calculated according to the formerly received boundaries of 
the Nearctic ‘* Region,” are certainly overstated, but means of arriving at a more 
accurate computation are not now forthcoming. 
A considerable majority of the Nearctic Families and genera 
seem to be generally distributed throughout the whole area, which 
we may fairly call a Subregion, and consequently its division into 
Provinces is not easily effected, their delimitations resting rather on 
differences of species than of higher groups. Of the many attempts 
to subdivide the Subregion, that of Baird! seems to be the most . 
successful. He long ago pointed out the existence of three Pro- 
vinces in its southern portion, the most easterly of which may be 
termed the ‘“ Alleghanian,” since it extends from the Atlantic 
across the mountains whence it is named, and over the valley of 
the Mississippi and its prairies to about long. 100° W. where the 
sterile plains begin. Then its boundary turns northward, crossing 
the Platte and intersecting the Missouri about Fort Lookout. 
1 “The Distribution and Migrations of North American Birds,” Am. Journ. 
Sc. and Aris, ser. 2, xli. pp. 78-90, 184-192, 337-347 (January, March, and May, 
1866). Reprinted /bis, 1867, pp. 257-293. German translation, Journ. fi Orn. 
1866, pp. 244-269, 338-352. 
* | make this assertion though aware of the views to the contrary expressed 
by Dr. Merriam in his ‘‘ Results of a Biological Survey of the San Francisco 
Mountain Region and Desert of the Little Colorado, Arizona” (North American 
Fauna, No. 8. Washington: 1890). He arrives (p. 24) at the conclusions ‘‘ that 
the whole of extratropical North America consists of but two primary life regions, 
a Boreal region, which is circumpolar; and a Sonoran or Mexican table-land region, 
which is unique.” The-first of these, it will be seen, supports my contention of 
the essential unity of the Nearctic and Palearctic areas. The second is one the 
probability of which I will not dispute; but I think that at present the facts 
adduced in its support are hardly sufficient to warrant its adoption by naturalists, 
who, not being Americans, must necessarily be acquainted with them only at 
second hand, especially as I am disposed to consider that Dr. Merriam’s enumera- 
tion (pp. 26-28) of the ‘‘causes which determine distribution,” however well they 
may fit the area of which he treats, may not be of universal application. 
